Biodiversity and palaeoecology of the Maastrichtian marine molluscs from the Paris Basin (France)

Since the first half of the 19th century, the limestones of Vertus Mont Aimé (Marne) and Bois d’Esmans (Seine-et-Marne) have been confused with the Danian pisolitic limestone and their malacological content has been the subject of partial lists. For the first time, the complete description of the malacofauna of these limestones is provided. Its study is based on recent samples (fieldtrips in 2014 and 2017) and a new examination of material collected by the previous authors. As a result, 57 taxa were recognised, including 31 formally identified species; nine species are in open nomenclature and the other taxa identified at the higher ranks. Among these, 14 species of gastropods, including a new genus and 5 species of bivalves, are newly described: ?Calliostoma monswavinarensis sp. nov., Sparnollonia bicarinata gen. et sp. nov., ?Tectus acmantensis sp. nov., ?Tectus fraterculus sp. nov., ?Tectus senarmonti sp. nov., ?Clypeostoma vertusensis sp. nov., Calliomphalus (Planolateralus) montenati sp. nov., Rhinoclavis parvisulcatus sp. nov., ?Vicinocerithium heberti sp. nov., Granulolabium cretaceum sp. nov., Haustator bergierensis sp. nov., Sveltella binkhorsti sp. nov., Fusinus bouchardae sp. nov., ?Pseudopisania cretacea sp. nov., Nucula bauti sp. nov., Arca (s. str.) submontensis sp. nov., Plicatula pacaudi sp. nov., Bathytormus sparnacensis sp. nov. and Chama loubryi sp. nov. This fauna was previously unknown from the Paris Basin or even from Northwestern Europe. With the exception of endemic taxa which are dominant, it shares significantly more species with the Maastrichtian of Limburg (28% of the assemblage) than with the Danian of the Paris Basin (9% of the assemblage). This allows it to be attributed to the Maastrichtian age, in accordance with other palaeontological data on ostracods, chondrichthyans, large benthic Foraminifera and mosasaurs discovered recently. The assemblages at Vertus and Mont Aimé indicate palaeoenvironments deposited under shallow waters (with some brackish elements), probably close to the coastline. Therefore, this study highlights the distinctive character of the faunal content of the limestones of Vertus Mont Aimé and Bois d’Esmans, which constitute a unique Maastrichtian formation in the Paris Basin and which can be called the Vertus-Mont Aimé-Esmans Formation.